This invention relates to a visual indicator for a fluid operated system and, more particularly, to an improved indicator which is responsive to relatively low actuating pressures applied thereto so as to selectively dispose predetermined indicia in an indicating position to thereby furnish an indication of the operating condition of the system.
In various types of fluid operated systems, such as in fluidic logic systems, fluidic control systems, or the like, there is a need to monitor various portions and components of the system so that suitable action can be taken should the necessity for same arise. For example, it is important to be apprised immediately of a system malfunction. Also, in a system wherein interrelated devices are used, and wherein the operation of the system is interdependent upon the respective devices, the respective operating conditions of critical devices should be monitored. Such monitoring is advantageous in field testing new or proposed systems and is invaluable during trouble-shooting and maintenance of fluidic systems.
In general, many of the indicating devices which previously have been used to monitor the operating conditions of a fluid operated system have been of the electrical or electromechanical type. These devices often added to the complexity of the fluid operated system and, in many instances, required substantial fluid-to-electrical or fluid-to-mechanical interface components in order to be operable.
Recently, various visual indicating devices have been proposed which are directly responsive to fluid flow or to a differential fluid pressure. Essentially, these devices are switches and are capable of exhibiting a first or a second state depending upon the fluid flow or differential pressure applied thereto. One such device is described in U.S. Pat. No. 3,528,384. This patented device includes a vane disposed within a housing, the vane being bidirectionally rotated depending upon the direction of fluid flow in the housing. Unfortunately, although the vane rotates in response to fluid flow between the fluid conduits in the device, there is no capability of sealing one or the other of the fluid channels as a result of this rotation. Consequently, this device suffers from the disadvantage of requiring fluid consumption during its operation. This consumption tends to limit the application of the indicating device to those systems wherein excessive fluid leakage is of no importance.
Another fluid condition indicating device has been proposed in U.S. Pat. No. 3,541,991. However, this device suffers from the same disadvantage as noted hereinabove in that there is no capability of sealing any of the fluid conduits. Hence, this device is accompanied by excessive fluid consumption. Moreover, this device does not readily provide respective indications of bidirectional fluid flow.
A still further indicator device for a fluid operated system is described in U.S. Pat. No. 3,643,620. This patented device is of a complex construction and requires the visual indicating mechanism to be mechanically separated from the fluid monitoring mechanism.
In addition to the foregoing defects, the prior art devices generally require a substantially high minimum actuating pressure to produce a change in the visual indication of the fluid operating condition. For example, such devices generally are not responsive to a fluid pressure less than about 15 psig.
Therefore, there has been a long-felt need for a fluid condition visual indicator which is of simple construction and which is not accompanied by excessive fluid leakage. Also, such a visual indicator should be responsive to very low actuating pressures, on the order of less than 1 psig.
Also, although it is common for visual indicators to be provided with indicia representing a fluid operating condition, it is believed that no visual indicator currently is available which provides graphic indicia directly representative of the particular fluid operating condition which is being monitored. Although graphic symbols have been used for many years to schematically represent the operation of fluidic components, it is believed that there has been no prior attempt to use these graphic symbols in conjunction with a fluidic monitoring visual indicator.